Infant attention consists of multiple phases, including stimulus orienting, sustained attention and attention termination. These phases index overall arousal/alertness functions of the brain, and modulate specific attention systems in the cortex. The PI has used heart rate as an index of the alertness/arousal system and shown the effects of attention on a wide variety of infant information processing systems. This has been done with behavioral methods to measure attention and with psychophysiological and neuroimaging methods to examine the effect of sustained attention on specific brain processes. A significant advance in the prior grant period was the development of tools to use infant structural MRIs for realistic models of the infant head and brain for cortical source analysis of ERP. The current project will use these tools to study the relation between sustained attention and brain areas involved in endogenously-cued spatial attention by identifying the generators of ERP components with cortical source analysis. The project also will examine the effects of attention on the cortical response to face stimuli. The tools developed in the prior grant period will be refined to improve the cortical source analysis, generalize the procedures to doing cortical source analysis in infants without structural MRIs, and generalized to other infant neuroimaging methods.